asio: Use internal ssl context and engine impl

Implement asio-ssl layer with three classes in asio::ssl::mbedtls:
* context -- replaces SSL_CTX, used mainly as a container to options,
certs, keys
* engine -- replaces SSL, implements the actual mbedtls operations
* bio -- implements openssl BIO specifically tailered to mbedtls and
its asio usage

Further updates:
* asio: Used shared_ptr<> for bio pairs
* asio: Add error checks to mbedtls-bio
* asio: Address potential ssl-context ownership issue
* asio: Address potential bio-engine ownership issue


* Original commit: espressif/esp-idf@d823106aa6

components/asio/port/mbedtls/include/mbedtls_error.hpp

@@ -0,0 +1,55 @@
+//
+// SPDX-FileCopyrightText: 2021 Espressif Systems (Shanghai) CO LTD
+//
+// SPDX-License-Identifier: BSL-1.0
+//
+#pragma once
+
+#include "asio/detail/config.hpp"
+#include "asio/ssl/error.hpp"
+#include "asio/ssl/detail/openssl_init.hpp"
+#include "mbedtls_context.hpp"
+
+namespace asio {
+namespace error {
+namespace detail {
+
+class mbedtls_category : public asio::error_category
+{
+public:
+    const char* name() const ASIO_ERROR_CATEGORY_NOEXCEPT
+    {
+        return "asio.ssl";
+    }
+
+    std::string message(int value) const
+    {
+        const char* s = asio::ssl::mbedtls::error_message(value);
+        return s ? s : "asio.mbedtls error";
+    }
+};
+
+} // namespace detail
+
+const asio::error_category& get_mbedtls_category()
+{
+    static detail::mbedtls_category instance;
+    return instance;
+}
+
+const asio::error_category& get_ssl_category()
+{
+    return asio::error::get_mbedtls_category();
+}
+
+} // namespace error
+
+namespace ssl {
+namespace error {
+
+const asio::error_category& get_stream_category()
+{
+    return asio::error::get_mbedtls_category();
+}
+
+} } } // namespace asio::ssl::error